Mercury relay container



April 7, 5 I. L. MITCHELL ETAL 3,

MERCURY RELAY CONTAINER Filed Jan. 31, 1962 INVENTORS Izvma. L. MiTCHELL. r\l\c-rora HOIZOUHTZ BY M M ATTORNEYS United States Patent M 3,128,353 MERCURY RELAY CGNTAENER Irving L. Mitchell, Roclrvilie Centre, and Victor Horowitz, Oceanside, N.Y., assignors to Ebert Electronics Corp, Floral Park, N.Y., a corporation of New York Filed Jan. 31, 1962., Ser. No. 170,174 15 Claims. (Cl. 200-112) This invention relates to containers for mercury relays and switches of the mercury displacing type, and more particularly to mercury relay and switch assemblies in which the container is comprised of a mixture of a polyamide such as nylon filled or impregnated with fiberglass material.

In prior art mercury relays and switches of the displacer type, the container has been fabricated of such materials as glass or metal. The disadvantages of using a glass container for a mercury relay are that the glass is readily breakable and diificult to seal. These factors decrease life and increase the costs of mercury relays. Due to the fact that glass is breakable, it is necessary to insure the delicate handling of relays as they are being assembled.

When metal is used as the material for a container in a mercury switch or relay, the metal must be insulated from the electrically conducting parts of the switch or relay. In addition, the metal is subject to corrosion. When a metal container is surrounded by an energizing coil, eddy current effects can occur for which compensation, such as shielding is required.

The use of ordinary synthetic molding compounds as materials for the container of a mercury relay has been studied but has hitherto been considered impractical, because known synthetic compounds have been ineffective in withstanding weather, corrosion and heat, and often become porous. Moreover, most synthetic compounds, especially thermoplastics, tend to absorb moisture, and such absorption of moisture causes dimensional instability. Another disadvantage found to exist in many synthetic compounds which were tested is that repeated sparking of contacts over a period of time causes the material of the container to corrode, crack or otherwise deteriorate, for reasons which are not clear.

It is known that a considerable number of synthetic compounds, including polymers, when filled or impregnated with fiberglass, have improved structural, physical and chemical properties. Some examples of these other compounds are polycarbonates, polystyrenes, styrenebutadienes and styrene acrylonitriles. In the patent to Bradt, 2,877,501, issued on March 17, 1959, the impregnation of casting resins such as those mentioned above by fiberglass strands or rovings is disclosed, for example, to improve the structural, physical and chemical properties thereof.

Superior results, however, have been obtained by impre nating or filling polyamide resins such as nylon 6 (polycaprolactam), nylon 610 (polyhexamethylene sebacamide) and nylon 66 (polyhexamethylene adipamide) with fiberglass strands or preferably rovings comprising 10% to 50% by weight of the total mixture. The above polyamide compounds are described in Man-Made Textile Encyclopedia, copyright 1959, by the Textile Book Publishers, Inc.

Nylon 6, nylon 610, nylon 66, and nylon 37X when impregnated with fiberglass material and used as the molding compound for a container on envelope of a mercury switch or relay, have been found to have high resistance to the deleterious effects of weather, heat and corrosion and have been found to withstand the destructive effects of making and breaking electrical contacts. In addition, the material has great structural strength, resists dimensional change due to heat, and has been 3,128,358 Patented Apr. 7, 1964 found to be substantially non-porous to gases and to mercury. Such envelopes, contrary to the expectations of those skilled in the art, have been found eminently suitable for commercial application as envelopes of mercury relays, whereas plastics generally have not proved satisfactory.

According to the present invention, the material of the mercury relay container is comprised of a polyamide such as nylon, which has been heat and light stabilized, and filled or impregnated with fiberglass material in the form of rovings to form a substantially homogeneous mixture relatively impervious to deleterious electrical, electromagnetic, and chemical effects. The percentage by weight of the fiberglass material in the total mixture may be of from 12 to 50%, but the most favorable percentage range has been found to be 30% to 40%. The polyamide used may be nylon 6, nylon 610, nylon 66 or nylon 37X. The nylon employed is heat and light stabilized.

It is known that fiberglass filled or impregnated nylon has excellent molding and machining qualities, very low shrinkage, high strength under compression and tension, high impact strength, a low coefficient of thermal expansion, and high resistance to the effects of acids and alkalies.

For example, as to structural strength, one known mixture of nylon 66 filled or impregnated with fiberglass rovings comprised about 30% to 40% by weight of the total mixture has about 2 /2 times the tensile strength of nylon 6 or 66 at 73 F.; about twice the impact strength of nylon 6 at 73 F.; about one-tenth the coefficient of linear thermal expansion of all polyamides; and at least ten times less deformation than nylon 66 under a load of 4000 psi. measured at 122 F. These facts in themselves do not, however, enable prediction as to suitability of the materials for use in mercury relays. Such devices are unpredictable by nature and their construction in-' volves art. The present invention is, therefore, in the nature of a discovery.

According to the invention, a polyamide such as nylon 66, nylon 6 and nylon 610 is impregnated with fiberglass by weight from 30% to 40% in the form of rovings and molded into the form of a container having at least one opening through which the operating elements of a mercury relay, including the mercury, may be inserted. The container may be molded in the form of a hollow receptacle to contain the mercury pool and the working elements of a mercury relay or switch. The particular form of the container will, of course, depend upon the desired operating relationship of the working elements and the mercury pool contained therein. It is not our intention to limit the scope of the present invention to a container for a mercury relay or a mercury switch wherein the container is of a particular design and the operating elements of the relay have a particular operating relationship; on the contrary, the container of the invention has general application to mercury switches and relays of the displacer type, the container being of a novel general form and of a particular material composition which when incorporated into a novel general form confers the above-stated and other advantages on mercury relays and switches and assemblies thereof.

Further, and according to the invention, after the op erating elements of the relay including the mercury pool are suitably positioned in the container, at least one closure in the form of a plug may be fitted into, and sealed to, the container near the open end so that the shape at the open end of the container forms raised walls or a well around the plug. The plug may be provided with a sealing tube therein through which an inert gas is introduced into the container.

In certain instances where design so requires, a plug to be fitted into the opening or openings of the hollow receptacle may have pre-fi-tted thereinto and sealed therewith one or more electrodes which, after the plug is fitted into the open end of the container, extend into the container for suitable contact with the mercury pool therein. Alternatively, one or more holes may be drilled into the plug, and the electrode or electrodes inserted therein and sealed with the plug at the same time the plug is sealed with the container.

As a further alternative, the container may be molded in the form of a hollow receptacle having as many openings therein as may be desired, said openings being subsequently closed and sealed. For example, the hollow receptacle may be formed to have a plurality of openings and a plug inserted and sealed as necessary at lower openings prior to the pouring thereinto of mercury to form a pool therein. Some of the openings may be molded to receive electrical conducting members or plugs in which electrical conductors are mounted while others may be molded to receive plugs.

It is, accordingly, an object of the invention to provide in a mercury switch or relay of the displacer type a container therefor which is rugged, non-corrosive, nonporous, non-conducting, non-magnetic, and which maintains its desired physical dimensions and properties over a long period of relay operation.

Another object of the invention is to provide in a mercury relay or switch of the displacer type a container therefor comprised of nylon impregnated or filled with fiberglass rovings or strands, said container having the property of being relatively unaffected by the production of nascent oxygen within due to sparking between the contacts and the mercury.

Yet another object of the invention is to provide in a mercury relay or switch of the displacer type acontainer comprised of fiberglass filled nylon and in the form of a hollow receptacle having as many openings as desired for receiving electrical conducting elements, and insertion of relay operating elements, said openings being sealed after insertion of the relay operating elements.

Another object of the invention is to provide for mercury relays or switches of the displacer type a container comprised of a homogeneous mixture of nylon in1pregnated or filled with fiberglass material in the form of rovings.

These and other objects will be better understood by referring to the drawing in which:

The single figure is a view in cross-section of a mercury relay having a container according to the invention.

Referring to :FIGURE 1, a mercury relay is shown having a container 112 which is comprised of a polyamide compound impregnated or filled with fiberglass material. The fiberglass material may be in the form of rovings impregnated in the polyamide to form a mixture therewith. The percentage by weight of the fiberglass rovings to the total mixture of poly-amide and fiberglass may be from to 50%, and the polyamide used may be compounds known as nylon 6, nylon 610, nylon 66 or nylon 37X. Other polyamide compounds may be used however, and the compound employed should be light and heat stabilized.

The container 12 may be molded in the desired form or shape of hollow receptacle, having at least one suitably sized opening therein, depending upon the particular relationship desired between operating elements of the relay and the container. The particular form of container according to the invention shown in the drawing is for purposes of illustration of the invention and not by way of limitation. The container 12 is in the form of a tube having an integral transverse wall 14 near the lower end thereof, said wall 14 being located as to form a well 16 in relation to the sides of the container 12.

If it is desired that an electrode be provided at the lower end of the container =12, an opening shown at 17 may be molded or drilled into the transverse wall 14 for ceive an electrode .36.

receiving an electrode, as The electrode 18 is sealed to the wall 14 by pouring into-the well 16, a quantity of epoxy resin fusible with the electrode 18 and with the material of container 12.

The reference numeral 2%! indicates operating elements of the mercury relay or switch generally, the particular operating elements and the spatial relationship thereof shown serving only as an exemplary illustration of a mercury relay or switch, and are not to be construed as a limitation on the type of mercury relay or switch for which the container 12 is to be used. It is to be further understood that although reference hereinbelow is to a mercury relay, the description applies equally to a mercury switch, the only difference therebetween being the mode of actuation thereof.

As an exemplary illustration, the operating elements 20 may include an armature or plunger 22 and a pool of mercury 24 displaced by said plunger when actuated by the relay energizing coil indicated at 26. The plunger 22 may be provided with radial protrusions 23 mounted on the sides of the plunger 22 or integral therewith, the pro trusions 23 being in sliding or guiding engagement with the inside surface of the container 12.

In the forming of the container 12, an interior shoulder as indicated at 28 may be molded near the end opening thereof in order to conveniently receive a plug 30, so located and dimensioned in relation to the walls of the container 1 2 at the opening, that a well is formed as indicated at 31. The plug 311 may be of any suitable synthetic compound, and a Kovar tube indicated at 32 is located therein through which container 16 may be evacuated or be provided with a special atmosphere by conventional methods. The plug 30 may be bonded to the container 12 as by epoxy resin or other suitable compounds bondable with both the plug 3% and the container 12, and this resin may cover the tube 3-2, which is separately sealed.

An aperture 34 may be drilled into the plug 30 to re- In the exemplary relay arrangement shown, it is desirable to provide the electrode 36 with an insulating covering over most of its length. The lower or contact end 36', of the electrode 36 is bare and is suitably fused or bonded to an insulating cup 38 surrounding the contact end 36 in spaced relationship there to so that contact between the electrodes '18 and 36 does not occur until the level of mercury pool 24 is displaced by the plunger 22, when actuated, sufificiently to exceed the level of the cup 38.

After the production of a vacuum or a special atmosphere such as inert gas in the container 12, epoxy resin indicated at 44 is poured into the well 31 thereby sealing the plug 3%} to the container 12, and sealing any electrodes not prebonded to the plug 30 thereto, said epoxy resin also covering the Ko-var tube 3 2.

If desired, the protrusions 23 may be of a self-lubricating material comprised of a polyamide containing a substantial amount of M08 in addition to fiberglass impregnated therein. The container 12 may also be comprised of this self-lubricating material. If either the protrusions 23 or the container 1 2, or both, are comprised of self-lubricating material such as described above or a similar selflubricating material, for example, tetrafluoroethylene, the weal on the protrusions 23 and the inside surface of the container 12 is greatly reduced due to the lower coefiic ent of friction between the protrusions 23 and the container 12, thus increasing the operating lifetime of the relay.

While the present invention has been described by reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without departing from the invention. Therefore it is the aim of the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What is claimed is:

1. A mercury relay of the displacer type comprising a container for said mercury relay, said container consisting of polyami-de impregnated with fiberglass and molded in the form of a hollow receptacle with at least one opening therein for insertion therethrough of the operating elements of the relay, electrical conducting means extending through, and sealed to, said hollow receptacle, closure means tor said at least one opening, said closure means being sealed to said hollow receptacle and a pool of mercury in said container for selectively electrically connecting said conducting means together.

2. Apparatus according to claim 1 wherein the hollow receptacle is in the form of an extended tube surrounding said at least one opening.

3. Apparatus according to claim 2 wherein the extended tube includes an interior shoulder for receiving said closure means.

4. A mercury relay of the displacer type comprising a container for said mercury relay, said container comprising entirely of a mixture of nylon filled or impregnated with fiberglass and molded in the form of a hollow tubular receptacle having a plurality of openings therein, electrical conducting means extending through at least one of said openings, closure means for at least one of said openings, said at least one opening means being sufficiently large to permit the insertion of operating elements of the mercury relay therethrough, and synthetic compound seals 'for all of said openings and a pool of mercury in said container for selectively electrically conmeeting said conducting means together.

5. A container for a mercury relay of the displacer type comprising a hollow receptacle comprised of nylon filled or impregnated with 30 40% fiberglass, said hollow receptacle including at least one opening therein through which operating elements of the relay are inserted, a plug for said opening, electrical conducting elements mounted in said plug and extending therethrough, a pool of mercury in said container for selectively electrically connecting said elements together, an aperture in said plug through which said hollow receptacle may be evacuated or be provided with a special atmosphere, and a quantity of synthetic compound for sealing said electrodes to said plug, said synthetic compound also sealing said aperture.

6. A container for electrical conducting elements comprising electrical contacts in said container, and a pool of mercury in said container for bridging said contacts to establish an electrical conducting path therebetween, said container comprising a hollow receptacle formed entirely of a material comprised of a polyamide filled with fiberglass, said hollow receptacle being arranged for the insertion therein of the electrical elements, and sealing means for sealing said hollow receptacle.

7. Apparatus according to claim 6 wherein said polyamide is polycaprolactam.

8. Apparatus according to claim 6 wherein said polyamide is polyhexamethylene sebacamide.

9. Apparatus according to claim 6 wherein said polyamide is polyhexamethylene adipamide.

10. Apparatus according to claim 6 wherein said fiberglass is in the form of rovings.

11. Apparatus according to claim 10 wherein said fiberglass rovings comprise 30% to 40 by Weight of said material.

12. In a mercury relay of the displacer type including a pool of mercury, a container for said pool of mercury, a plurality of spaced electrical contacts located in said container, a plunger in said container for displacing the mercury pool to effect bridging and unbridging said contacts, said container consisting essentially of a polyamide impregnated with 10-50% fiberglass rovings.

13. Apparatus according to claim 12 including protrusions mounted on said plunger for sliding engagement with with the inside surface of said container, said protrusions being comprised of self-lubricating material.

14. Apparatus according to claim 13 wherein said selflubricating material includes a polyarnide filled with fiberglass and a substantial amount of M08 15. Apparatus according to claim 12 wherein said material includes a substantial amount of M08 References Cited in the file of this patent UNITED STATES PATENTS 2,264,841 Gallagher Dec. 2, 1941 2,590,930 Butterworth Apr. 1, 1952 2,973,417 McKinney Feb. 28, 1961 

1. A MERCURY RELAY OF THE DISPLACER TYPE COMPRISING A CONTAINER FOR SAID MERCURY RELAY, SAID CONTAINER CONSISTING OF POLYAMIDE IMPREGNATED WITH FIBERGLASS AND MOLDED IN THE FORM OF A HOLLOW RECEPTACLE WITH AT LEAST ONE OPENING THEREIN FOR INSERTION THERETHROUGH OF THE OPERATING ELEMENTS OF THE RELAY, ELECTRICAL CONDUCTING MEANS EXTENDING THROUGH, AND SEALED TO, SAID HOLLOW RECEPTACLE, CLOSURE MEANS FOR SAID AT LEAST ONE OPENING, SAID CLOSURE MEANS BEING SEALED TO SAID HOLLOW RECEPTACLE AND A POOL OF ME 